Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns. 

Inspecting and servicing your portable generator's spark plug

This article provides a guide to inspecting and servicing your portable generator's spark plug, including how to inspect the spark plug gap and when to replace it. 

 

Environment

This article applies to most portable generators. 

 

Contents

1. What is the spark plug gap?
2. Where to purchase spark plugs.
3. What type of spark plug do I need?
4. Inspecting the spark plug.
5. Spark plug condition and when to replace.

 

Spark Plug Gap

What is the spark plug gap, and why is it important?

• The spark plug gap is a small space between the tipo of the center electrode and the ground electrode of the spark plug. The spacing of the gap is important because it determines how far the spark has to jump to ignite the air-fuel mixture to the engine. If the gap is no longer in specification, it can lead to combustion issues. 

 

How do I know what my spark plug gap is?

• The spark plug gap will vary by the type of spark plug. The type of spark plug and there for the gap distance will vary by unit. The owner's manual lists the spark plug part number and gap dimensions. 
• Where can I download a user manual for my Generac portable generator?

 

What type of spark plug and where to purchase

What type of spark plug can I use?

• Only use the recommended spark plug type; see the owner's manual product specifications section. 

 

Where can I purchase spark plugs for my portable generator?

• Spark plugs can be purchased through your local Generac Independent Authorized Service Dealer (IASD) or through Generac's Online Parts Store. 

 

Inspecting the spark plug

Step-by-step guide

To service spark plug: 

1. Clean the area around the spark plug
2. Remove and inspect the spark plug. 
3. Inspect the electrode gap with the feeler gauge and reset the spark plug gap. 
4. Install the spark plug finger tight, and tighten an additional 3/8 to 1/2 turn using the spark plug wrench. 
   
   

 

Understanding spark plug condition and when to replace

• In general, replace the spark plug if electrodes are pitted or burned or if the porcelain is cracked. When in doubt, it is best practice to replace the spark plug. 

 

Spark plug condition and troubleshooting

• Normal Condition: The firing end of the spark plug is typically light gray or brown; this is a good indication that the spark plug is in good condition.
• Dry or Wet: The spark plug is considered fouled if its firing end is covered in black dry carbon soot or black wet carbon covering. This may be due to issues with the spark plug insulation.
• Overheating: If the spark plug has been overheated, the insulator tip at the firing end will appear melted, glazed, or glossy. Replace the spark plug. 
• Deposits: Replace the spark plug if it accumulates a noticeable deposit on the firing end. This may be due to poor fuel quality or oil leakage. 
• Breakage: Replace the spark plug if it is physically damaged and there is visual breakage. This may be due to rapid heating or cooling of the metal causing breakage.